U.S. patent application number 11/912145 was filed with the patent office on 2008-08-07 for tough, long-lasting dental composites.
This patent application is currently assigned to Fraunhofer-Gesellschaft zur Forderung der angewandten Forschung e. V.. Invention is credited to Carsten Gellermann, Werner Storch, Herbert Wolter.
Application Number | 20080187499 11/912145 |
Document ID | / |
Family ID | 36655091 |
Filed Date | 2008-08-07 |
United States Patent
Application |
20080187499 |
Kind Code |
A1 |
Wolter; Herbert ; et
al. |
August 7, 2008 |
Tough, Long-Lasting Dental Composites
Abstract
A dental composite containing a nanoparticulate filler has a
resin matrix with structural element (Ib) ##STR00001## R is an
open-chain and/or cyclic alkylene, arylene, or alkylene arylene
with 1-10 C, optionally modified by oxygen, sulfur, carboxyl or
amino, R.sup.1 is an open-chain and/or cyclic alkylene, arylene, or
alkylene arylene with 1-10 C, optionally modified by oxygen,
sulfur, carboxyl or amino; R' is an open-chain and/or cyclic alkyl,
alkenyl, aryl, alkyl aryl, or aryl alkyl with 1-20 C; B and B' are
identical or different and are a straight-chain or branched
organically polymerizable group with (meth)acrylate residue;
R.sup.3 are identical or different and a bond to another Si or
hydrogen, alkyl with 1-10 C, or a bond to another metal atom; a is
1 or 2 and b is 0 or 1.
Inventors: |
Wolter; Herbert;
(Tauberbischofsheim, DE) ; Gellermann; Carsten;
(Gerbrunn, DE) ; Storch; Werner; (Hoechberg,
DE) |
Correspondence
Address: |
GUDRUN E. HUCKETT DRAUDT
SCHUBERTSTR. 15A
WUPPERTAL
42289
omitted
|
Assignee: |
Fraunhofer-Gesellschaft zur
Forderung der angewandten Forschung e. V.
Munchen
DE
|
Family ID: |
36655091 |
Appl. No.: |
11/912145 |
Filed: |
April 19, 2006 |
PCT Filed: |
April 19, 2006 |
PCT NO: |
PCT/EP2006/003585 |
371 Date: |
October 20, 2007 |
Current U.S.
Class: |
424/49 |
Current CPC
Class: |
C08L 83/16 20130101;
C08L 83/16 20130101; C08L 83/16 20130101; C08L 83/16 20130101; C08L
83/16 20130101; C08L 83/16 20130101; A61K 6/17 20200101; A61K 6/20
20200101; A61K 6/30 20200101; A61K 6/30 20200101; A61K 6/20
20200101; C08G 77/26 20130101; Y10S 977/919 20130101; A61K 6/896
20200101; A61K 6/30 20200101; A61K 6/20 20200101; A61K 6/896
20200101; A61K 6/896 20200101 |
Class at
Publication: |
424/49 |
International
Class: |
A61K 8/30 20060101
A61K008/30; A61Q 11/00 20060101 A61Q011/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 20, 2005 |
DE |
10 2005 018 351.4 |
Claims
1.-15. (canceled)
16. A dental composite comprising: (A) a matrix comprising a resin
with the following structural element (Ib) ##STR00019## wherein the
residues and indices have the following meaning: R is an open-chain
and/or cyclic alkylene group, arylene group, or alkylene arylene
group with 1 to 10 carbon atoms, respectively, and is optionally
interrupted by one or several oxygen or sulfur atoms or carboxyl or
amino groups or optionally carries such atoms/groups at an end
remote from the silicon atom; R.sup.1 is an open-chain and/or
cyclic alkylene group, arylene group, or alkylene arylene group
with 1 to 10 carbon atoms, respectively, substituted with the
urethane group shown in the formula (Ib), and is optionally
interrupted by one or several oxygen or sulfur atoms or carboxyl or
amino groups or optionally carries such atoms/groups at one end; R'
is an open-chain and/or cyclic alkyl group, alkenyl group, aryl
group, alkyl aryl group, or aryl alkyl group with preferably 1 to
20 carbon atoms; B and B' are the same or different and have the
meaning of a straight-chain or branched organically polymerizable
group with at least one (meth)acrylate residue and thus at least 3
carbon atoms; R.sup.3 are the same or different, wherein at least
some of the R.sup.3 have the meaning of a bond to another silicon
atom and, when not a bond to another silicon atom, are a hydrogen
atom, an alkyl group with 1 to 10 carbon atoms, or a bond to
another metal atom that can be incorporated into silicic acid
hetero polycondensates; a is 1 or 2 and b is 0 or 1; and (B) is a
nanoparticulate filler.
17. The dental composite according to claim 16, further comprising
a polymerization initiator.
18. The dental composite according to claim 17, wherein the
polymerization initiator is selected from the group consisting of
initiators for radical curing, initiators for thermal curing, and
initiators for radiation curing.
19. The dental composite according to claim 16, wherein at least
one of B and B' contains one or two methacrylate groups or is a
methacrylate residue.
20. The dental composite according to claim 16, wherein B and
optionally B' are methacrylate acid ester groups of trimethylol
propane, of glycerine, of pentaerythrite, of C.sub.2-C.sub.4
alkanediols, of polyethylene glycols, of polypropylene glycols, or
of optionally substituted and/or alkoxylated bisphenol A.
21. The dental composite according to claim 16, wherein B and
optionally B' comprise methacrylate acid ester groups of
trimethylol propane, of glycerine, of pentaerythrite, of
C.sub.2-C.sub.4 alkanediols, of polyethylene glycols of
polypropylene glycols, or of optionally substituted and/or
alkoxylated bisphenol A. or comprise these esters.
22. The dental composite according to claim 16, wherein R.sup.1 is
a C.sub.1-C.sub.6 alkylene group substituted with a urethane
group.
23. The dental composite according to claim 16, wherein structural
elements of the resin are comprised to at least 60 mole % of the
structural elements of the formula (Ib).
24. The dental composite according to claim 16, wherein structural
elements of the resin are comprised predominantly of the structural
elements of the formula (Ib).
25. The dental composite according to claim 16, wherein structural
elements of the resin are comprised exclusively of the structural
elements of the formula (Ib).
26. The dental composite according to claims 16, wherein the
nanoparticulate filler is comprised of approximately spherical
particles with narrow diameter distribution or contains such
spherical particles with narrow diameter distribution.
27. The dental composite according to claim 26, wherein the
nanoparticulate particles have essentially a diameter between 10 nm
and 200 nm.
28. The dental composite according to claim 16, further comprising
an additional filler.
29. The dental composite according to claim 28, wherein the
additional filler is selected from macrofillers of glass, ceramic
or quartz with particle sizes between 2 .mu.m to 50 .mu.m;
homogenous microfillers in particular of pyrogenic silica;
inhomogeneous microfillers, preferably in the form of chipped
polymerisates in particular mixtures of pyrogenic silica and Ba
glass or Sr glass with particle sizes in the range of approximately
1 .mu.m to 5 .mu.m; dental glasses with particle diameters of
approximately 1 .mu.m to 5 .mu.m: mixtures of these fillers; hybrid
fillers; or very fine hybrid fillers.
30. The dental composite according to claim 16, containing a total
filler amount of between 1 wt. % and 50 wt. % consisting of the
nanoparticulate filler and an optional additional filler.
31. The dental composite according to claim 30, wherein between 5
wt. % and 60 wt. % of the total filler amount is the
nanoparticulate filler.
32. The dental composite according to claim 31, wherein between 29
wt. % and 35 wt. % of the total filler amount is the
nanoparticulate fillers.
33. The dental composite according claim 16, containing a total
filler amount between 70 wt. % and 90 wt. % consisting of the
nanoparticulate filler and an optional additional filler.
34. The dental composite according to claim 33, wherein between 5
wt. % and 60 wt. % of the total filler amount is the
nanoparticulate filer.
35. The dental composite according to claim 34, wherein between 29
wt. % and 35 wt. % of the total filler amount is the
nanoparticulate fillers.
36. The dental composite according to claim 16, in the form of a
composite material, fastening material, cement, filling material,
adhesive, coating material, fissure sealant, tooth neck coating,
crown or bridge material, or bonding.
Description
[0001] The present invention relates to dental composites with
improved properties. The composites are produced by employing
fillers and silicic acid hetero polycondensates the latter at least
partially comprised of a basic scaffold that has at least two
(meth)acrylate residues per silyl unit wherein at least one of
these (meth)acrylate residues is bonded by a urethane group.
Starting materials (silane compounds) suitable for the present
invention are disclosed among other compounds in DE 103 49 766.8
which, at the time of filing the instant application, had not been
made publicly accessible.
[0002] In the past, a plurality of plastically processable
composites based on organic monomers (for example, mono, di, tri or
even higher methacrylates) in combination with commercially
available fillers (for example, x-ray opaque dental glasses, highly
dispersed silica, or the like) for use as dental restoration
materials have been developed and have found acceptance in the
market. However, the physical properties that are partially still
unsatisfactory include e.g. abrasion that is too high, shrinkage
during curing that is too high and leads to marginal gap formation
particularly when subjected to chewing loads, x-ray absorption that
is too minimal, aesthetic flaws as well as an allergenic potential
(as a result of residual monomers). First significant advances in
this regard have been achieved by employing inorganic-organic
hybrid polymers (ORMOCER.RTM.) as a result of their dual character
as matrix systems. Corresponding composites for dental applications
are disclosed e.g. in patent application DE 41 33 494. Accordingly,
it is possible to realize many important individual
properties/requirements.
[0003] The realization of all important individual demands
(shrinkage, aesthetics, marginal gap seal-tightness, abrasion
resistance, bio-compatibility, x-ray opacity and optionally others)
in combination, i.e., in one material type and at a significantly
increased overall property level as a prerequisite for a
significantly increased "service life" of restoration and
prophylactic measures however has not been achieved with the
materials currently available. Moreover, a further aspect
increasingly gains importance, i.e., the bio-compatibility of the
dental materials. For example, residual monomers that remain as a
result of incomplete curing of the composite and that subsequently
will slowly leak from the material can cause allergies in a
patient. Moreover, often it would be desirable that the materials
are already free of monomers in the state in which they are
delivered to the dental office in order to prevent possible
allergies in the dental assistant or the dentist.
[0004] It is an object of the present invention to find a remedy
and to provide new composites as well as their use in the dental
field, for example, for restorations, prophylactic measures,
prosthetics, orthodontics.
[0005] This object is solved by providing dental composites in
accordance with claim 1 as well as uses according to claim 15.
Accordingly, excellent conditions are provided to realize today's
desire for restorative and prophylactic measures with a
significantly increased "service life" while providing optimal
aesthetics and bio compatibility. The hybrid matrix which is the
basis of the composites is comprised of resin systems containing
(meth)acrylate groups that, for example, are disclosed in DE 103 49
766.8 already mentioned supra. They can be obtained either by
hydrolytic condensation of silane compounds that can be produced by
isocyanate addition to an OH-group containing compound.
Alternatively, they can be produced by hydrolytic condensation of
hydroxyl group containing silane compounds and subsequent reaction
of the thus obtained resin with an appropriate isocyanate compound
containing at least one (meth)acrylate group. A further important
component of the composite in addition to the resin system is a
nanoparticulate, optionally functionalized, filler that will be
explained in more detail in the following.
[0006] The basis for the resin systems from which the composites
according to the present invention can be produced are structural
elements of the formula (Ib)
##STR00002##
wherein the residues and indices have the following meaning:
[0007] R is an open-chain and/or cyclic alkylene group, arylene
group, or alkylene arylene group with 1 to 10 carbon atoms,
respectively, which in some cases can be interrupted by one or
several oxygen or sulfur atoms or carboxyl or amino groups for can
carry such atoms/groups at their end that is remote from the
silicon atom.
[0008] R.sup.1 is a substituted open-chain and/or cyclic alkylene
group, arylene group, or alkylene arylene group with 1 to 10 carbon
atoms, respectively, that, in some cases, can be interrupted by one
or several oxygen or sulfur atoms or carboxyl or amino groups or
can carry such atoms/groups at one of their ends and, as can be
seen in the formula, is substituted with a urethane group that
carries B'.
[0009] R' is an open-chain and/or cyclic alkyl group, alkenyl
group, aryl group, alkyl aryl group, or aryl alkyl group with
preferably 1 to 20 carbon atoms; in this context, reference is
being had also to the further explanations in regard to the
function of this group that can be found in connection with the
definition of the formula (II) described infra.
[0010] B and B' can be the same or different; both residues have
the meaning of a straight-chain, branched, or cyclic organic group
that has at least one (meth)acrylate residue and therefore has at
least 3 and preferably up to 50 carbon atoms. At least one of the
residues B and B' in a preferred embodiment can have, in addition
to the aforementioned first acrylate group or methacrylate group, a
second or even a second and a third Michael system which, in turn,
can also be, but must not be, an acrylate group or methacrylate
group. Worth mentioning are residues B and B' that comprise as
structural elements C.sub.2 to C.sub.4 alkanediols, the trimethylol
propane group, the pentaerythrite group or the glycerol structure.
B and B' can be acrylic acid ester groups and or methacrylic acid
ester groups of trimethylol propane, of glycerine, of
pentaerythrite, of C.sub.2 to C.sub.4 alkanediols, of
polyethyleneglycols, of polypropylene glycols, or of bisphenol A,
optionally substituted and/or alkoxylated, or can comprise these
esters. Also preferred is also the embodiment in which B and B'
represent only one (meth)acrylate group that is bonded by an ester
bond of the carboxyl residue to the remaining molecule. B and B'
can have a continuous carbon skeleton, the carbon chain(s) (main
chain and/or side chain(s)) can however also be interrupted by
hetero atoms or groups such as O, S, SO, NH, NHCO, PR, POR, CONHCO,
COO, NHCOO or the like. The carbon skeleton of B and B' can be
exclusively aliphatic, in particular with open and/or closed
structures, B and B' can however also comprise one or several
aromatic core(s) or condensed systems or triazine groups or the
like, for example, bisphenol A structures or the like. Moreover,
the groups or structures can be substituted in any way, for
example, with acid groups, acid amide groups, ester groups or amino
groups.
[0011] The residues R.sup.3 bonded to the silicon atom can be the
same or different. At least one part thereof must have the meaning
of a bond to another silicon atom, optionally instead partially
also to another metal atom that can be incorporated into the
silicic acid hetero polycondensates. In many cases, not all
residues R.sup.3 will have this meaning, and in this case some of
them instead will be a hydrogen atom, i.e., the silicon atom will
carry one or several hydroxy groups. In the case that 4-a-b is 3,
on average approximately 30% to 70%, i.e., up to approximately two
of the three groups OR.sup.3 can be hydroxy. When 4-a-b is 2, the
number of groups OR.sup.3 that are not crosslinked can be on
average up to approximately 50%. In the case of 50%, on average one
of the two groups is crosslinked with a further silicon atom or
metal atom. In some of the aforementioned cases, some of the groups
R.sup.3 can have instead of hydrogen also an alkyl group with 1 to
10, preferably 1 to 4, carbon atoms. By means of the proportion of
residues that represent bonds to further Si atoms or other metal
atoms, the degree of condensation of the (partial) condensate is
defined at least in as much as can be represented by the above
formula (Ib).
[0012] a means 1 or 2, preferably 1, and b can be 0 or 1.
[0013] R.sup.3 is preferably a residue with 1 to 4 carbon atoms
and, particularly preferred, methyl or ethyl or a bond to a further
Si atom.
[0014] These silicic acid polycondensates or partial condensates
can be produced in a first synthetic pathway suitable for the
present invention by hydrolytic condensation from silanes of the
formula (Ia):
##STR00003##
wherein the residues B, B', R.sup.1 and R' have the meaning as
provided supra for formula (Ib) and wherein X is a group that can
undergo hydrolytic condensation reactions by forming Si--O--Si
bridges. Groups X are referred to as inorganic crosslinking agents
because by the hydrolytic condensation reaction a silicic acid
polycondensate network can be formed. Accordingly, it is apparent
to a person skilled in the art which meaning X can have.
Preferably, X is a C.sub.1-C.sub.10 alkoxy group, even more
preferred a C.sub.1-C.sub.4 alkoxy group, and especially preferred
methoxy or ethoxy. X can also be, as needed, a halide such as Cl,
hydrogen, hydroxy, acyloxy with preferably 2 to 5 carbon atoms,
alkylcarbonyl with preferably 2 to 6 carbon atoms, or alkoxy
carbonyl with preferably 2 to 6 carbon atoms. In some cases. X can
also be NR'' with R'' being hydrogen, alkyl with preferably 1-4
carbon atoms or aryl with preferably 6-12 carbon atoms.
[0015] Preferred for the present invention are silicic acid
polycondensates with the aforementioned structural element (Ib)
wherein B has the meaning B''-Z- and Z is --O--R.sup.4,
--S--R.sup.4, --NH--R.sup.4, --C(O)O--R.sup.4, --O--, --S--, --NH--
or --C(O)O--. R.sup.4 can have the meaning alkylene, arylene, or
alkyl arylene with preferably 1 to 10 carbon atoms (in the case of
groups without rings) or 6 to 14 carbon atoms (for groups with
rings). B'' is in this connection like B a straight-chain or
branched organic group with at least one (meth)acrylate group and
up to preferably 50 carbon atoms.
[0016] The silicic acid poly (partial) condensates with the
structural element of the formula (Ib) can optionally also be
derived from a mixture of different silanes of the formula (Ia) in
which the residues B and/or B' have different meanings. In these
condensates the residues B and/or B' do not have a uniform meaning.
Since B in these condensates, on the one hand, can have the meaning
as defined for B', but, on the other hand, can also have a meaning
that is different therefrom, the formula (Ib) encompasses silicic
acid poly (partial) condensates in which all residues B and B' have
the same meaning; silicic acid poly (partial) condensates in which
B and B' have a different meaning but all residues B and all
residues B' represent the same residue, respectively; and silicic
acid poly (partial) condensates in which the residues B' have a
meaning different from B and the residues B and/or the residues B'
each are mixtures of different residues. Alternatively, or in
addition, these condensates can contain foreign metal atoms that
can be incorporated by condensation into such systems, for example,
boron, aluminum, germanium, tin, titanium or zirconium. The metals
that are suitable for this purpose are known to a person skilled in
the art. In the case of silicic acid poly (partial) condensates
containing foreign metals the substances are referred to as hetero
silicic acid poly (partial) condensates.
[0017] It should be mentioned that the components B and B' in the
silicic acid (partial) condensates with the structural element (Ib)
used in the present invention must not necessarily be present in
stoichiometric ratios relative to one another as can be derived
from the structural element itself. As can be taken in the
following from the description and the examples, for example, the
residue B' can be present in a substoichiometric quantity. In these
cases, the poly (partial) condensate still contains free (or
"capped" or "protected" as a result of rearrangement) hydroxy
groups; this, as disclosed above, affects the viscosity behavior of
the resin.
[0018] The structural elements of the present invention are
therefore silanes and silicic acid poly (partial) condensates
derived therefrom that comprise a partially or completely
hydrolyzable/hydrolyzed and/or condensable/condensed silane
residue, at least one urethane group and at least two residues that
are in a branched arrangement and contain (meth)acrylate groups so
that they are organically polymerizable wherein one of them is
bonded by means of the aforementioned urethane group to the silicon
atom. All three molecule parts can be utilized for the purpose of
property modifications in accordance with the annual report of the
Fraunhofer Institut fur Silicatforschung 1992, pp. 61-72 and
Polymer+Materials Research Symposium 1993, Bayreuth, pp. 14-17. In
this connection, the additional organically polymerizable group
that has been introduced via the urethane group provides an
additional crosslinking possibility by means of the organic
residues in comparison to the silicic acid polycondensates of DE 44
16 857 C1 so that harder polymers can be obtained.
[0019] As will be explained in the following in more detail, the
silanes and the silicic acid poly (partial) condensates derived
therefrom can be obtained from silanes that have a residue B as
well as a hydroxy group that is bonded to a linker between this
residue B and the silicon atom. They are disclosed in DE 44 16 857
C1. When comparing the systems that are obtained by direct
condensation of such silanes with those of the present invention,
it is apparent that the hydrophilicity of the matrix of the system
according to the invention in comparison to that of the systems
according to DE 44 16 857 C1 is reduced because none or, when some
of the original hydroxy groups have not been reacted, only a
reduced number of free OH groups are present so that wet-resistant
(hydrolytically more resistant) less viscous resins with reduced
sensitivity relative to moisture are obtained. On the other hand,
by means of the variability of the residues B, B', R, R.sup.1 and
R' a high variability can be achieved that leads to special or new
property combinations. A further advantage of the present invention
resides in that condensates can be produced that are free of
starting monomers and, based thereon, organic polymers (by
polymerization of the organically polymerizable groups) with
excellent mechanical properties and minimal shrinkage can be
obtained that have viscosity properties ensuring excellent
processing possibilities. Such polymers are referred to in the
following as polymerisates when they are free of fillers and as
composites when they are containing fillers.
[0020] By means of the organically polymerizable portions
(primarily the (meth)acrylate groups) of the residues B and B' the
aforementioned silicic acid polycondensates can be organically
crosslinked. In this connection, because of the presence of at
least two organically crosslinkable groups per silane molecule, a
system is obtained that is generally free of starting materials
whose organic proportion leads to an especially high mechanical
strength as well as, surprisingly, an improved shrinkage behavior
with reduced shrinkage. According to the invention, these systems
can be used in combination with nanoparticulate filler and
optionally additional fillers as dental composites with extremely
advantageous properties.
[0021] Accordingly, based on the aforementioned resins,
inorganic-organic polymers with excellent mechanical properties
(for example, minimal shrinkage) are obtained that are completely
or essentially free of the monomers used as starting materials,
wherein the resins themselves as a result of, for example, their
beneficial viscosity properties enable excellent processing
possibilities. These polymers are provided in the form of
composites (i.e., containing fillers, wherein at least one
essential proportion of the filler or fillers are nanoparticulate
fillers) and are suitable, as a result of their beneficial
properties with regard to toxicological considerations (for
example, because of their high bio-compatibility) in combination
with high hydrolytic resistance and very minimal shrinkage,
especially in the field of dentistry.
[0022] The composites according to the present invention can be
adjusted with regard to rheological properties before curing as
needed. For example, by adding monomeric additives (for example,
reactive thinners) the flowability of the materials can be
increased so that they are suitable as fissure sealers or the like.
For other application purposes such as fillings prostheses,
materials of higher viscosity are required instead. In this way,
different applications in the dental field can be realized, for
example, for the purposes indicated supra. The composites have a
high abrasion resistance (with regards to wear caused by chewing
and antagonist wear). As needed, a high x-ray opacity can be
imparted in that they contain appropriate x-ray opaque fillers.
[0023] The compounds and (partial) condensates that are suitable
for use in the present invention are obtainable, for example, based
on the compounds of the formula II
##STR00004##
wherein B, R.sup.1, R, R', X, a and b have the meaning as indicated
for the formulas (Ia) and (Ib) and wherein Y is OH. The
substituents or residues R' and X on the silicon atom can be
selected arbitrarily. In the literature a lot has been reported in
regard to the inorganic-organic materials containing silicon atoms,
for example, those that are available commercially under the name
"ORMOCER.RTM.", with respect to the respective properties that are
imparted by the respective silane residues to the condensate or the
organically polymerizable network so that in this connection no
detailed explanations are needed. X indicates the hydrolyzable
residues. With these groups that are also referred to as inorganic
crosslinkers, in cooperation with optionally present organic
crosslinkers, i.e., in particular the organically polymerizable
groups of the residues B and optionally B', physical properties of
the network that is formed can be adjusted, such as hardness or
flexibility or thermal expansion coefficient. The groups R' that
are usually not organically polymerizable, are referred to as
network modifier; several properties can be affected with their
selection. A person skilled in the art therefore is aware which
meaning X can have. Preferably, X is a C.sub.1-C.sub.10 alkoxy
group even more preferred a C.sub.1-C.sub.4 alkoxy group, and
especially preferred methoxy or ethoxy. However, X can also be, as
needed, a halogenide such as Cl, hydrogen, hydroxy, acyloxy with
preferably 2 to 5 carbon atoms, alkyl carbonyl with preferably 2 to
6 carbon atoms, alkoxy carbonyl with preferably 2 to 6 carbon
atoms, optionally also NR'' with R'' being hydrogen, alkyl with
preferably 1 to 4 carbon atoms, or aryl with preferably 6-12 carbon
atoms, or another suitable leaving group.
[0024] Compounds of the formula (II) are known. Compounds of the
formula (II) can be produced, for example, according to DE 44 16
857 C1 in which B has the meaning B''-Z- wherein B'' can also have
the meaning of a straight-chain or branched organic group with at
least one (meth)acrylate group and up to preferably 50 carbon atoms
with the preferred embodiments for B as described. For example,
when reacting epoxide silanes with compounds B''(AH) in which AH is
a hydroxy group, a mercapto group, or amino group or carboxylic
acid residue, a product is obtained in which Y is --OH and Z is
--O--R'', --S--R'', --NH--R'', --C(O)O--R'', --O--, --S--, --NH--
or --C(O)O--. R'' has the aforementioned meaning. The reaction is
realized usually in the presence of a suitable catalyst, for
example, tertiary amines such as triethylamine or phosphines such
as triphenylphosphine and optionally at elevated temperatures.
[0025] In the afore described reactions for producing the compounds
of the formula (II), it is possible that isomers of these compounds
are produced depending on the actually employed starting materials.
This is in particular the case to a considerable amount when the
residues X are alkoxy groups, primarily methoxy or ethoxy groups.
Because in such isomers the group Y is partially involved in the
isomerization/transesterification reaction, it is partially no
longer free in these products. However, it was found that these
byproducts can be utilized just as well as the compounds of the
formula (II) themselves for the production of the silicic acid poly
(partial) condensates that are used to prepare the composites of
the present, wherein a separation of the different products is not
even necessary. It is instead sufficient to react the starting
materials described for the preparation of the compounds of the
formula (II) in the described way and to subsequently subject them
to hydrolysis. Surprisingly, the group Y is then set free again
while the back formation of SiOH groups takes place to different
degrees and can be essentially suppressed. Therefore, in general a
condensate with an Si--O--Si network is obtained.
[0026] The compounds of the formula (II) or their condensation
products with liberated group Y are processed as needed (for
example, separated, washed, isolated) and/or, if needed, dried. In
particular it should be taken care optionally that no or if
possible only few H-active contaminants are present in the reaction
mixture in order to avoid in the reaction to be described in the
following side reactions with the isocyanate. Subsequently, they
are reacted with isocyanate containing at least one (meth)acrylate
group and a product results in which a second (meth)acrylate group
is present that is bonded by a urethane group --NH--C(O)O--.
[0027] When monomer compounds of the formula (II) are reacted, in
general silanes of the formula (Ia) will be obtained. They can be
subjected subsequently to hydrolytic condensation in order to
obtain condensates of the formula (Ib).
[0028] The preparation of the silane compounds discussed above in
connection with the afore described pathway for preparing the
resins can be realized in different ways. In the following, some
method variants will be explained in principle.
[0029] In a first embodiment of the invention, in a first step of
the preparation a compound B''(COOH), wherein B'' has the above
meaning, is reacted with a silane in
[CH.sub.2--CH(O)]--R--Si(X).sub.3 containing an oxirane ring in
which R and X have the meaning as set forth for formulas (Ia), (Ib)
and (II). Preferably, X is a methoxy group, ethoxy group, propoxy
group, or butoxy group. R can be, for example,
--CH.sub.2--O--(CH.sub.2).sub.3. The reaction is realized
preferably in the presence of a catalyst as explained above and at
elevated temperatures. As described above, in this reaction,
depending on the starting material and the reaction conditions, not
only compounds of the formula (II) are produced but also, or even
exclusively, condensation products (transesterification products),
for example, by loss of an alcohol molecule or by formation of
bridge bonds between the oxygen atom of the hydroxy group that is
being formed (the group Y in the formula (II)) and a silicon atom,
in accordance with the following schematic illustrating as an
example the reaction of methacrylic acid with 3-glycidyloxypropyl
trimethoxysilane ("glymo"):
##STR00005##
[0030] The above schematic shows an intermolecular rearranged
product. It should be clear that, of course, the products of
intramolecular condensation or transesterification reactions can be
used also.
[0031] The product or product mixture, inasmuch as the OH groups
are not completely hydrolyzed, can be subjected to hydrolysis that
effects inter alia condensation of the silane residues.
Surprisingly, when X is an alkoxy group, free hydroxy groups on the
silicon atoms are not necessary produced in significant quantities
while the hydroxy group at the position Y is formed. As already
described above in general, the formation of free hydroxy groups on
the silicon atom can be adjusted and, as needed, can be suppressed
essentially. Accordingly, a silicic acid polycondensate or partial
condensate can be obtained that, to a very large extent, optionally
predominantly, or even completely, contains the following
structural element (III)
##STR00006##
wherein the indicated residues and indices have the above explained
meaning.
[0032] The above explained hydrolysis however will often not be
necessary. This is so because the silylation of the hydroxy group
can optionally protect it. When in the reaction mixture partially
free and partially protected OH groups are present, it is easy to
produce a condensate of the formula (Ib) in which the residues B'
in relation to B are present in a deficient amount. That this may
be desirable has been explained above.
[0033] In an alternative preparatory pathway for the hetero
polysiloxane that can be used as a component of the dental material
according to the present invention, the first step is the reaction
of a compound B''(OH), wherein B'' has the above meaning, with a
silane [CH.sub.2--CH(O)]--R--Si(X).sub.3 containing an oxirane ring
in which R and X have the meaning indicated above for the formulas
(Ia), (Ib), and (II), Preferably, X is a methoxy group, ethoxy
group, propoxy group, or butoxy group, R can be, for example,
--CH.sub.2--O--(CH.sub.2).sub.3. The reaction is carried out
preferably in the presence of a catalyst as explained above and at
elevated temperatures according to the following schematic
illustrating as an example the reaction of HEMA (hydroxy ethyl
methacrylate) with 3-glycidyloxypropyl trimethoxysilane
("glymo"):
##STR00007##
[0034] As explained above, in this reaction, depending on the
starting material, not only a component of the formula (II) but
also, or even exclusively, condensation products can be produced,
for example, by loss of an alcohol molecule and formation of a
bridge bond between the oxygen atom of the hydroxy group that is
being formed (the group Y in the formula (II)) and a silicon atom,
Accordingly the following transesterifications are possible for
this reaction in principle.
##STR00008##
[0035] The next step of preparing the condensates can be realized
as described in the following. The product of the first step is
reacted with a compound B'NCO wherein B' has the above described
meaning. In this ways a compound of the formula (Ia) or a
condensate with the structural element (Ib) is produced.
[0036] The two-stage synthesis of the silane resins suitable for
the purposes of the present invention will be explained in more
detail in the following with the aid of a few schematics.
##STR00009##
##STR00010##
##STR00011##
##STR00012##
[0037] In the following, the preparation of compounds of the
formula (Ia) will be explained moreover with the aid of a few
selected reactions.
##STR00013## ##STR00014## ##STR00015##
[0038] The above schematics illustrate that, according to DE 103 49
766.8, in the context of isocyanate addition silanes of a very
variable structure can be produced. For example with the product of
the reaction of (meth)acrylate with glymo that is known from DE 44
16 857 C1 silanes of the formula (Ia) can be produced that,
depending on the employed reaction partner, can have relatively
long or relatively short connecting chains between the double bonds
of the residues B and B' (see upper half of the first page of
schematics). The same patent also discloses the product of the
reaction of hydroxyethylmethacrylate (HEMA), succinic anhydride,
and glymo. This product contains a single methacrylic acid residue
as well as a relatively remote hydroxy group. Based on this,
compounds with two methacrylate groups can be produced between
which very long or extremely long connecting chains can be
arranged. In the middle of the second page of schematics, the
reaction of compounds with two groups containing double-bonds (here
methacrylate groups) and positioned relatively close together as
well as a third double bond-containing group (here also a
methacrylate group, but it could be also a different double-bond
containing group) farther removed from the two groups is
illustrated by means of an example.
[0039] For the purposes of the present invention, silanes of the
formula (Ia) or silicic acid poly (partial) condensates that are
not yet completely condensed and have structural elements according
to formula (Ib) are partially, largely or completely hydrolyzed or
condensed alone or optionally also with further silanes and/or
silicic acid (partial) condensates. For this purpose, on the one
hand silanes and (partial) pre-condensates derived therefrom that
are co-condensable but not co-polymerizable or those that also have
a polymerizable groups are suitable. Of course, the additional
components can be admixed at an earlier stage as long as they do
not undergo undesirable side reactions with isocyanates. In this
way, condensates with exclusively the structural units of the
formula (Ib) according to the invention or inorganic networks with
Si--O--Si units result that contain these structural units in
combination with other units. Co-condensable or co-polymerizable
compounds or (partial) pre-condensates can be preferably reacted in
a molar ratio of up to 80%, relative to the monomer units (silyl
residues or polymerizable compounds) of which the resulting resin
or polymer is built. Especially preferred is an addition in a molar
ratio of up to approximately 20%.
[0040] Co-polymerizable components can be added, instead or
additionally, to the silanes of the formula (Ia) as well as not yet
completely condensed silicic acid poly (partial) condensates with
structural elements of the formula (Ib); the co-polymerizable
components are, for example, compounds that can be polymerized by
radical and/or ionic and/or covalent-nucleophilic polymerization.
Compounds to be added that can be polymerized by radical
polymerization are, for example, those with C.dbd.C double bonds
such as acrylates or methacrylates wherein the polymerization is
realized by means of the C.dbd.C double bonds. Ionically
polymerizable compounds to be added contain, for example, ring
systems that can be polymerized by cationic ring-opening
polymerization for example, spiroorthoesters, spiroorthocarbonates,
bicyclic spiroorthoesters, monoepoxides or oligoepoxides or
spirosilanes, as those known e.g. from DE 41 25 201 C1. It is also
possible to add compounds that can polymerize ionically or by
radical polymerization, for example, methacryloyl spiroorthoester.
The latter can be polymerized by radical polymerization by means of
the C.dbd.C double bond and cationically by ring-opening
polymerization. The preparation of these systems is disclosed, for
example, in Journal f. prakt Chemie, Vol. 330 (2) 1988, pp.
316-318. Moreover, it is possible, for example, to add other known
silane-bonded cyclic systems that can also be incorporated by
polymerization. Such systems are, for example, those that contain
epoxides. Such systems are disclosed in connection with the
preparation of spirosilanes in DE 41 25 201 C1. The aforementioned
components are incorporated by polymerization during the
polymerization reaction of the resins by means of their organically
polymerizable groups so that a copolymer resin of the silanes and
copolymers according to the invention is obtained whose silane
groups are hydrolytically condensed with one another or with other
groups. The aforementioned components can be preferably added in a
molar ratio of up 20%, relative to the monomer units (silyl
residues or polymerizable compounds) of which the resulting resin
or polymer is built. However, it is especially preferred to keep
the composites of the present invention and thus also the basic
organically polymerizable resins free of monomers.
[0041] As mentioned above, in an alternative synthetic pathway for
preparing the resin systems according to the present invention, the
compounds of the formula II can be used which are first
hydrolytically condensed before the reaction with a (meth)acrylate
group-containing isocyanate is carried out. With the exception of
this reversal, the aforementioned explanations also apply to this
pathway of the preparation of the resin system.
[0042] The silicic acid poly (partial) condensates with structural
elements of the formula (Ib) that are utilizable for the purposes
of the present invention have, when Y is reacted completely or at
large proportions, a low hydrophilicity of the matrix and therefore
will absorb only little water in a moist/wet environment. Their wet
strength is improved. The residues B and B' can be incorporated
alone or in mixtures and/or co-condensates with other components as
mentioned above into organic polymer structures or they can be
crosslinked as such by these groups. As a result of the additional
organic crosslinkable group or the additional silyl group that
carries B', a general increase of the strength of the crosslinked
products can be achieved. In particular, composites that are filled
at a low level or high level, are obtainable that are made from
resins with relatively minimal viscosity and that have a very
minimal shrinkage. Their suitability as dental compounds should be
underscored in particular, especially in configurations that are
free of monomers and are thus toxicologically/allergenically
innocuous and have generally moreover a high wet strength as well
as further advantageous properties as mentioned already supra.
[0043] For obtaining the dental composites the silicic acid poly
(partial) condensate with structural elements according to formula
(Ib) is mixed before organic curing with one or several additives
and/or fillers.
[0044] An important component in this regard are nanoparticulate
fillers or a combination of such fillers of different size or
different composition, optionally in combination with further known
fillers such as particulate dental glasses, for example, Ba--Sr
aluminumborosilicates. The term "nanoparticulate" is to be
understood as the fillers having a diameter or having a greatest
diameter in the range of less than 1,000 nm. In the case that the
fillers have a relatively broad particle size distribution, at
least 90% of the mass of the filler should be below this limit.
According to the present invention, the term "nanoparticulate"
filler is meant to include also sub-nanoparticulate fillers whose
size can extend down to the size of the so-called clusters.
Preferred are nanoparticulate fillers with approximately spherical
shape. Even more preferred are fillers with diameters in a range of
10 nm to 400 nm, even more preferred in a range of 10 nm to 100 nm.
It is moreover preferred to employ each individual filler with a
very narrow particle size distribution.
[0045] The nanoparticulate fillers can be present individually,
i.e., in isolated form, as agglomerates, aggregates, or polymer
resins. Preferred is that they are used in a non agglomerated,
non-aggregated form.
[0046] The materials for the aforementioned fillers are not
critical and are selected as needed. Well suited are, for example,
those fillers that are used in the publications DE 196 43 781, DE
100 41 038, or DE 100 18 405. Well suited are SiO.sub.2 particles
that can be obtained in accordance with known so/gel methods and
that then have a very narrow diameter distribution. These but also
nanoparticles of different composition can be surface-modified, for
example, silanized, in order to match their surface properties to
those of the matrix.
[0047] The nanoparticulate fillers can be used alone or in
combination with other fillers for the purposes of the present
invention. Employable as additional fillers are, for example,
macrofillers (for example, made from glass, ceramics, or quartz,
particle sizes between 2 .mu.m to 50 .mu.m), homogenous
microfillers (for example, made from pyrogenic silica, particle
sizes approximately 0.02 .mu.m to 0.06 .mu.m, preferably
approximately 0.04 .mu.m), inhomogeneous microfillers (for example,
a portion of the pyrogenic silica is present as chipped
polymerisate), hybrid fillers (mixtures of macrofillers and
microfillers) or very fine hybrid fillers (for example, mixtures of
aerosil and Ba glass or Sr glass with particle sizes in the range
of approximately 1 .mu.m to 5 .mu.m). Well suited for the present
invention are, for example, dental glasses with particle diameters
of approximately 0.4 .mu.m to 20 .mu.m, preferably of approximately
1 .mu.m to 5 .mu.m.
[0048] The ratio of fillers relative to one another can be selected
arbitrarily. Beneficial are weight proportions of the
nanoparticulate fillers of approximately 5 wt. % to approximately
60 wt. % relative to the total weight of the fillers in the
composite. Especially beneficial are proportions of more than 5 wt.
% to 30 wt. %. In such embodiments, the nanoparticulate fillers can
be located in the cavities or gaps of closed packed, possibly even
approximately close (sphere) packed, larger filler particles, in
particular when the larger filler particles have an approximately
spherical shape. It was found that when using proportions in this
range, particularly highly filled composites can be obtained that
have a particularly minimal shrinkage and particularly high
abrasion resistance.
[0049] Depending on the desired application, the filler can be
added in very different total quantities. For example, on the one
hand, it can be present in a proportion of 50 wt. % of the
composite or even significantly higher and in particular in a
proportion of 70 wt. % to 90 wt. % of the composite wherein higher
or highest filled composites are required for example, for fillings
or the like; on the other hand, for lower-level or low-level filled
compositions, e.g., fissure sealants, coatings for tooth necks, the
filler is present in a proportion of less than 50 wt. %, e.g., 1
wt, % to 50 wt. % and preferred approximately 1 wt. % to 20 wt.
%.
[0050] In regard to obtaining high contents of fillers and
excellent processing (for example, reducing the viscosity)
optionally the use of filler pre-polymerisates is possible also,
i.e., nanoparticulate and/or conventional fillers that are coated
with a polymer matrix (in accordance with the present invention or
a different one for example, a purely organic one) that are present
in the form of cured composite spheres or composite chips.
[0051] Depending on the provided special application, the composite
can also have added to it suitable additives such as initiators,
coloring agents (dyes or pigments), oxidation inhibitors,
polymerization inhibitors (for preventing a premature
polymerization), leveling agents, UV absorbers, stabilizers,
microbicidal agents, or the like as they are known to a person
skilled in the art. Examples of polymerization initiators are
initiators for radical polymerization and in particular for thermal
curing such as peroxides (for example, dibenzoyl peroxide) or photo
initiators such as benzophenone, camphor quinone, or combinations
of .alpha.-diketones with amines as reducing agent, as e.g.
disclosed in DE 199 03 177 C2. For dual curing of systems that are
polymerizable by radical polymerization and cationic
polymerization, diaryliodonium salts or tiarylsulfonium salts can
be added in particular; the aforementioned publication also
provides examples therefor.
[0052] The resulting plastically processable composites are
distinguished thus in that they can have very variable filler
contents and, at the same time, can be processed excellently. This
enables advantageously their use in the field of dental
restoration/prophylaxis (for example, for fillings, fissure
sealants, and the like). The cured composites show inter alia a
high strength and a high E modulus that can be matched or
approximated to the respective application (for example, dentine
has an E modulus of approximately 18 GPa or in liquid approximately
10 GPa). The same holds true for the thermal expansion coefficient
.alpha. that for dentine is approximately at 8.times.10.sup.-6
K.sup.-1. Moreover, they have a drastically increased abrasion
resistance which keeps wear by chewing very minimal. Moreover,
surprisingly they shrink upon curing (the organic crosslinking
action) only minimally, as mentioned above (see examples).
Moreover, they have, when required, high x-ray opacity which is
achievable primarily by incorporating appropriate x-ray opaque
fillers, in particular the aforementioned dental glasses and
nano-particulate fillers of which many have a high x-ray opacity.
Details in this regard are known to a person skilled in the art.
For example, an exchange of SiO.sub.2 particles for
SiO.sub.2/SnO.sub.2 particles provides a significant increase of
x-ray opacity. And finally, the composites according to the
invention provide excellent aesthetics because the basic resin in a
large number of embodiments is essentially colorless or
translucent, which is self-evident in particular based on
matched/approximated refractive indices of resin and filler
particles and based on the particle distribution in their size.
[0053] The filled dental composite (i.e. the organically not yet
crosslinked filled resin), after it has been applied in accordance
with the indicated purpose, for example, applied to a dental cavity
or filled into a mold that corresponds to a future prosthesis, can
be organically crosslinked in a suitable way and thus cured. In
this connection, primarily an organic polymerization of the
(meth)acrylate groups is suitable. This is a radical polymerization
that usually is carried out by adding radical starters as mentioned
above and optionally known activators with exposure to light such
as light in the visible range (blue light, dental curing light),
i.e., photochemically, thermally, or redox-induced. Depending on
the further additives added to the resin, as mentioned above,
additional photo chemical, thermal, or chemical (for example by
means of self-curing two-component reactions, anaerobic, redox,
ionic, covalent-nucleophilic) induced reactions can take place by
means of which the resin matrix will be crosslinked to an even
narrower mesh structure. For example, the combination of self
curing action with, for example, photoinduced or thermal curing is
possible.
[0054] The composites according to the present invention exhibit as
a result of the components that can be mutually matched to one
another not only excellent data with regard to the individual
properties but also an excellent overall profile of properties and
thus significant advantages relative to the classic composites
based on methacrylate-containing monomers (see, for example,
composite 1 and 2 in the table of Example 3 infra). This is so
because the matrix with regard to rheological properties and
strength can be adjusted optimally to the field of application
while the nanoparticulate fillers can be optimally selected with
regard to their diameter, their x-ray absorption, their surface
functionality and the like. Composites result with filler contents
that can be higher than in the "classic" materials and, in this
connection, can have a very high volume proportion in the composite
with extremely minimal shrinkage, with (abrasion) strengths that
match that of the neighboring natural materials, in general without
this requiring that thinners (i.e., monomers) be added for
processing.
[0055] In the following the invention will be explained with the
aid of exemplary embodiments in more detail.
EXAMPLE 1
Prior Art
[0056] This example explains the preparation of a monomer-free
resin system that contains free OH groups, based on a component of
the formula (II) with b equal 0; the latter is disclosed also in DE
103 48 766.8
1st Stage: Reaction of 3-Glycidyl Oxypropyl Trimethoxysilane
(Glymo) with Methacrylic Acid (MAS)
##STR00016##
[0057] To an amount of 199.1 g (0.802 mol) 3-glycidyloxypropyl
trimethoxysilane in a dry atmosphere (oxygen) triphenylphosphine as
a catalyst, BHT as a stabilizer, and subsequently 75.76 g (0.88
mol) methacrylic acid are added dropwise and stirred at 85.degree.
C. (approximately 24 h). The reaction can be monitored by the drop
in carboxylic acid concentration by means of acid titration as well
as epoxide conversion by means of Raman spectroscopy/epoxide
titration. The characteristic band of the epoxide group of epoxy
silane appears in the Raman spectrum at 1,256 cm.sup.-1. The
epoxide conversion or carboxylic acid conversion is at .gtoreq.99%
or .gtoreq.89% (.fwdarw.because 1:1.1 excess carboxylic acid).
2nd Stage: Hydrolysis/Condensation
##STR00017##
[0059] After adding acetic ester (1,000 ml/mol silane) and H.sub.2O
for hydrolysis with HCl as a catalyst, the reaction mixture is
stirred at 30.degree. C. The course of hydrolysis can be monitored
by water titration, respectively. Processing is done after
approximately several days of stirring by extracting several times
with aqueous NaOH and subsequent extraction with water and
filtration by means of a hydrophobic filter. Then, solvent is
removed by means of a rotary evaporator and subsequently by oil
pump vacuum in order to remove alcohol and water. A resin is
obtained that without use of so-called reactive thinners
(additional liquid monomers) is liquid and has a very minimal
viscosity (approximately 4-6 Pas at 25.degree. C. (strongly
dependent on the precise hydrolysis and processing conditions). The
CO.sub.2H contents was measured to be 0.00 mmol/g, i.e., the resin
contains no free monomeric methacrylic acid molecules anymore.
EXAMPLE 2
[0060] This example explains the reaction of the resin system of
Example 1 with isocyanate.
##STR00018##
[0061] To an amount of 73.9 g (0.28 mol) of the above resin in a
dry atmosphere (oxygen) at room temperature with stirring 30.41 g
(0.20 mol) methacrylic acid isocyanate ethyl ester was added
dropwise and the mixture stirred at 30.degree. C. The reaction can
be monitored by decrease of the OCN band by means of IR spectrum.
The characteristic band for the OCN group appears in the IR
spectrum at 2,272 cm.sup.-1. A viscous resin resulted having a
viscosity of approximately 18-25 Pas at 25.degree. C. (strongly
dependent on the precise synthesis and processing conditions in
particular also of the pre-stages). [0062] IR data:
v.sub.(OH.rarw.educt).apprxeq.3,500 cm.sup.-1 (residual OH because
the reaction was carried out with only 0.7 mol proportions of
methacrylic acid isocyanate ethylester) [0063]
v.sub.(NH.rarw.urethane).apprxeq.3,373 cm.sup.-1 [0064]
v.sub.(C=O.rarw.methacrylate/urethane).apprxeq.1,721 cm.sup.-1
[0065] v.sub.(C=C.rarw.methacrylate).apprxeq.1,638 cm.sup.-1
[0066] In the following, some properties of the matrix system
according to Example 1 (without reaction with isocyanate) are
compared with those of the matrix system according to Example
2.
TABLE-US-00001 Matrix System Matrix System (Example 1) (Example 2)
break strength [MPa] 70-80 103-115 stored 1.5 days at 40.degree. C.
under dry conditions E modulus [GPa] 1.7-1.9 2.2-2.5 shrinkage
[vol-%] (15 min) 54 4.2-4.6 cytotoxicity [% active cells] after
95-97 97-102 24 h
[0067] The comparison shows that the organic components of the
matrix system according to the invention has improved properties in
comparison to the resins used in the prior art; strength and the E
modulus are significantly increased and shrinkage is significantly
reduced.
EXAMPLE 3 AND COMPARATIVE EXAMPLES
a) Composite Preparation and Characterization
[0068] The incorporation of different filler types into the
described resin system after addition of conventional photo
initiators as well as further dental additives is carried out in
accordance with conventional methods by using different mixing
device types at different temperatures and optionally under
vacuum.
[0069] The resulting composites are placed into a rod mold
(2.times.2.times.25 mm.sup.3). The methacrylate groups are reacted
by a photo-induced radical polymerization so that the respective
composite is cured. By means of a 3-point bending test after 1.5
days of storage in air or water at 40.degree. C. the E modulus as
well as the break strength (at room temperature) of the resulting
rods are determined.
[0070] The shrinkage values of the composites are determined by
means of buoyancy flotation method (composite 3) or by means of
mercury dilatometer (comparative composites 1 and 2) for a
photo-induced radical polymerization.
[0071] The in vitro cytotoxicity test is carried out by means of
growth inhibition test in a microtiter plate on 3T3 mouse
fibroblasts with composite eluates at the MHH Hannover.
[0072] The abrasion was determined in a 3-media abrasion machine
according to the ACTA method.
[0073] The x-ray opacity was measured according to EN ISO 4049 with
an x-ray device type Polydoros SX80 of the Siemens company and
ultraspeed films of the Kodak company. The determination of the
degree of firm blackening was done by means of a dosimeter Lullus
1.21 (photo densitometer) of the Wellhofer company.
[0074] The thermal expansion coefficient .alpha. was measured and
evaluated by means of a dilatometer 402 E/7 of the Netzsch company
in a temperature range of 5.degree. C. to 50.degree. C.
b) Composite Data
[0075] In the following, the material characteristic data of two
commercially available filler composites (composites 1 and 2) are
listed in comparison to a composite 3 based on the matrix system
according to Example 2 in combination with standard fillers and a
composite 4 according to the present invention based on the matrix
system according to Example 2 with nanoparticulate fillers.
TABLE-US-00002 Composite 1 Composite 2 Composite 3 Composite 4
Filler mixture Ba--Al borosilicate Ba--Al borosilicate glass/
Ba--Al borosilicate glass, Ba--Al borosilicat glass, glass/highly
Ba--Al fluorosilicate highly dispersed silica, all SiO.sub.2
particles (60 nm), dispersed silica glass/ytterbium trifluoride;
fillers silanized SiO.sub.2/SnO.sub.2 core-shell highly dispersed
silica particles (80 nm), all silanized) Particle size [.mu.m]
0.04-2.0 0.04-3.0 0.04-3.0 0.06-3.0 Filler contents [wt. %] 75.0
80.0 77.0 82.0 Filler contents [vol. %] 56.5 60.0 60.4 67.7 Bending
strength [MPa] 118.9 (.+-.11.2) 116.0 (.+-.12.5) 132.0 (.+-.9.0)
145.0 (.+-.9.0) (24 h/37.degree. C., according to ISO 4049) E
modulus [MPa] 8,150 (.+-.385) 8,750 (.+-.360) 11,100 (.+-.300)
11,300 (.+-.300) (24 h/37.degree. C., according to ISO 4049)
shrinkage [vol. %]; 2.99 3.07 2.2 1.3 30 min. value x-ray opacity
220 380 .ltoreq.250 311 [% Al].sup.4) abrasion.sup.5) 58 66 48 30
Monomers BISGMA BISGMA.sup.1) free of monomers free of monomers
UDMA UDMA.sup.2) TEGDMA TEGDMA.sup.3) Thermal expansion 49.8 47.5
n.a. 26.9 coeffizient .alpha. (5-50.degree. C.) [10.sup.-6K.sup.-1]
cytotoxicity, 3T3 cells 24 h 88.5 (.+-.8.6) 96.6 (.+-.8.3) 99.4
93.0 [% vital cells after 48 h 93.0 (.+-.4.1) 86.4 (.+-.2.1) 98.6
99.6 incubation time]:
.sup.1)2,2'-bis[4-(3'-methacryloyl-oxy-2'-hydroxylpropoxy-phenyl]propane
.sup.2)7,7,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-dio-
xy-dimethacrylate .sup.3)triethyleneglycol dimethacrylate
.sup.4)according to ISO 4049 .sup.5)according to ACTA method
[.mu.m] (3 media abrasion)
[0076] The resin system upon which the composite 1 is based has a
shrinkage of greater than 7% and is in this regard therefore
significantly less favorable than the resin of Example 2.
[0077] A comparison of the composites 3 and 4 shows the advantages
of incorporating nanoparticulate fillers into the composite: for
the same resin matrix a significantly increased filler contents is
possible, the strength of the composite is greater, the shrinkage
is drastically reduced, the x-ray opacity is significantly
increased, and the abrasion is significantly reduced.
[0078] By replacing the SiO.sub.2 particles (60 nm) in composite 4
with SiO.sub.2/SnO.sub.2 particles (80 nm) the x-ray opacity can be
increased from 311 to 361% Al.
[0079] The nanoparticulate filler proportion effects a
significantly increased filler contents and in this connection in
particular a very high volume proportion in the composite wherein
the composite still enables easy application, i.e., it has an
adjusted flow behavior. The results are a surprisingly significant
reduction of shrinkage at 1.3% by volume in combination with a
drastically reduced abrasion behavior results, a high strength, an
E modulus that is approximated to that of dentine (E modulus
approximately 18 GPa or in liquid approximately 10 GPa; .alpha.
approximately 8*10.sup.-6K.sup.-1) as well as an approximated
thermal expansion coefficient, a high x-ray absorption (greater
250% Al is desired), excellent translucence (important for optical
appearance of the filling), and excellent bio-compatibility
(according to cytotoxicity test). As demonstrated by composite 4, a
monomer-free embodiment is possible which, for example, with regard
to allergenic exposure already during application, i.e., in the
uncured state, is of particular importance for the dental office
staff.
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